As a result of the volatility of gasoline and diesel fuels, in the fuel tanks of motor vehicles fuel vapors form which must be dissipated to prevent the generation of overpressure in the fuel tank. For reasons of emission prevention, the dissipated fuel vapors are generally routed through an activated charcoal filter which absorbs the volatile hydrocarbons. The remaining air is released into the environment.
In order to facilitate the removal of fuel from the fuel tank, it must be possible at the same time to aerate the fuel tank. Many motor vehicles moreover have devices for monitoring the tightness of the fuel tank so that leaks can be detected early. For purposes of leak diagnosis, air is conventionally pumped into the fuel tank by means of a pump until a specified overpressure arises. If the overpressure cannot be built up or if the overpressure diminishes again too quickly, there is a leak in the fuel system. The leak diagnosis device can then deliver a corresponding warning to the driver.
In particular, the air which has been fed into the tank within the framework of leak diagnosis must be filtered to protect the pump of the leak diagnosis system against particles.
Aeration and ventilation lines for the fuel tank are generally made separately since the requirements with respect to the positioning of aeration and ventilation openings are different. The aeration opening must be mounted at a moisture-protected site, while the ventilation opening must be at a site from which the emerging gases can be easily released into the environment. On the tank side, there is generally only a single opening for the two systems. This tank-side opening is connected to the aeration opening or the ventilation opening as needed by means of a three-way valve.
The object of this invention is to make available a device of the initially mentioned type which is especially compact and space-saving.